1. Field of the Invention
This invention relates to a process cartridge having a latent-image-bearing member on the surface of which a toner image is to be formed and an intermediate transfer belt which are integrally provided, an image-forming apparatus having such a process cartridge, and an intermediate transfer belt of the process cartridge.
2. Related Background Art
Image-forming apparatus making use of an intermediate transfer belt, which is a beltlike intermediate transfer member, are effective as full-color image-forming apparatus and multi-color image-forming apparatus in which a plurality of color timer images are sequentially superimposingly transferred to a transfer medium to output an image-formed material.
Compared with a transfer system as disclosed in Japanese Patent Application Laid-Open No. 63-301960, i.e., an image-forming apparatus in which toner images are transferred from an electrophotographic photosensitive member serving as a first image-bearing member to a transfer medium as a second image-bearing member, fastened or attracted onto a transfer drum, the above image-forming apparatus have an advantage that a variety of transfer media can be selected without regard to their width and length, including thin paper (40 g/m2 paper) and up to thick paper (200 g/m2 paper) such as envelopes, post cards and labels. This is because the use of the intermediate transfer belt makes any processing or control (e.g., the transfer medium is held with a gripper, attracted, and made to have a curvature) unnecessary for the transfer medium.
In addition, the intermediate transfer member made in the shape of a belt enables effective utilization of space to make the apparatus main body compact and achieve cost reduction, because the freedom in disposing it inside the image-forming apparatus can be greater than a case in which a rigid cylinder, such as an intermediate transfer drum, is used.
However, in usual cases the intermediate transfer belt has a shorter lifetime than the apparatus main body, and hence, under the existing conditions, it is indispensable to replace the belt in the middle of the use of apparatus. It is also necessary to dispose of the developer (hereinafter often xe2x80x9ctonerxe2x80x9d) having remained on the intermediate transfer belt. In addition to these disadvantages, it is necessary to replace many component parts such as a latent-image-bearing member, a developing assembly and a developer.
As a method of making these replacement parts into a unit or units so as to be attached to or detached from the main body with ease, it is proposed as disclosed in Japanese Patent Application Laid-Open No. 8-137181 that the intermediate transfer belt and the latent-image-bearing member are made into units independent from each other and are so placed as to be attached to or detached from the main body with ease.
However, such a means requires replacement units in a large number and makes user""s operation troublesome. Also, since the units are designed and placed independently from each other, a problem may arise such that the apparatus must be made large-sized and may involve a high cost.
As a means for solving such a problem, as disclosed in Japanese Patent Applications Laid-Open No. 6-110261, No. 10-177329 and No. 11-30944, a means is proposed in which the intermediate transfer belt and the latent-image-bearing member are made into one unit so as to be simultaneously attached to or detached from the main body and replaced.
However, as being different from a case in which the intermediate transfer belt is set at the time the apparatus main body is installed, such a method in which the intermediate transfer belt and the latent-image-bearing member are set up as one unit to provide a process cartridge which can be attached to or detached from the main body with ease tends to cause some problems due to the fact of making them into one unit. One of them is the problem that the latent-image-bearing member may be triboelectrically charged because of any vibration such an intermediate transfer belt/latent-image-bearing member integral cartridge (process cartridge) may undergo during distribution in the market. Once the latent-image-bearing member has been triboelectrically charged because of such vibration during distribution, the latent-image-bearing member may change in characteristics to cause density differences in the images to be reproduced.
In particular, with progress of techniques for image-forming apparatus in recent years, it has become possible for digital-development type printers and copying machines to develop minute and accurate latent images with a resolution of 600 dpi or more as exposure spots have been made smaller in size and more highly dense, and in addition thereto to obtain images with a high quality level on account of, e.g., precise control of electric fields. As the result, such unauthorized triboelectric charging of latent-image-bearing members during distribution that has not come into question in the past may also greatly affect image quality, and it is an important subject to solve this problem. This problem may especially remarkably occur when the latent-image-bearing member has a cylindrical rigid body as its support, because the intermediate transfer belt and the latent-image-bearing member tend to come into contact with each other with a stronger force than when the latent-image-bearing member is in the form of a belt. Moreover, this problem may much more remarkably occur when the latent-image-bearing member has an outer diameter of 50 mm or less.
In all the above proposals, however, any measure is taken against the triboelectric charging of latent-image-bearing members because of the vibration during distribution in the state they are taken out of the image-forming apparatus, and it can not be said that any apparatus have been designed taking distribution channels into account. Hence, there occur problems that the management cost may increase because of, e.g., any restriction on how to handle process cartridges after manufacture and that complaints from users may increase.
In addition to these, it is also an important subject to reduce running cost, and much more cost reduction must be achieved on the intermediate transfer belt and intermediate transfer belt/latent-image-bearing member integral cartridge which come to be replacement parts. Also, in order to make them easy to handle, the miniaturization and the disposal of waste toner must well be taken into consideration.
Accordingly, an object of the present invention is to provide a process cartridge, an image-forming apparatus and an intermediate transfer belt which promise easy maintenance, enable miniaturization and cost reduction of the apparatus, and yet can prevent any faulty images from being caused by the unauthorized triboelectric charging of latent-image-bearing members during distribution, and produce good images even when they are transported or left over a long period of time.
To achieve the above object, the present invention first provides a process cartridge which is detachably mountable to the main body of an image-forming apparatus; the process cartridge integrally comprising:
a latent-image-bearing member having a cylindrical rigid body as a support, on the surface of which an electrostatic latent image is formed and the electrostatic latent image is developed to form a toner image; and
an intermediate transfer belt to which the toner image formed on the latent-image-bearing member is primarily transferred and on which the toner image is held and transported to transfer the toner image secondarily to a transfer medium;
the latent-image-bearing member having a surface potential Vt of xe2x88x92200 Vxe2x89xa6Vtxe2x89xa6200 V when the intermediate transfer belt and the latent-image-bearing member are rubbed with each other.
The present invention, second, provides a process cartridge which is detachably mountable to the main body of an image-forming apparatus, the process cartridge integrally comprising:
a latent-image-bearing member having a cylindrical rigid body as a support, on the surface of which an electrostatic latent image is formed and the electrostatic latent image is developed to form a toner image;
an intermediate transfer belt to which the toner image formed on the latent-image-bearing member is primarily transferred and on which the toner image is held and transported to transfer the toner image secondarily to a transfer medium; and
a spacer member being provided between the intermediate transfer belt and the latent-image-bearing member, and the latent-image-bearing member having a surface potential Vt of xe2x88x92200 Vxe2x89xa6Vtxe2x89xa6200 V when the spacer member and the latent-image-bearing member are rubbed with each other.
The present invention, third, provides a process cartridge which is detachably mountable to the main body of an image-forming apparatus, the process cartridge integrally comprising:
a latent-image-bearing member having a cylindrical rigid body as a support, on the surface of which an electrostatic latent image is formed and the electrostatic latent image is developed to form a toner image; and
an intermediate transfer belt to which the toner image formed on the latent-image-bearing member is primarily transferred and on which the toner image is held and transported to transfer the toner image secondarily to a transfer medium,
the process cartridge having a means for lowering the contact pressure of the intermediate transfer belt against the latent-image-bearing member, to lower the contact pressure of the intermediate transfer belt against the latent-image-bearing member when the process cartridge is transported.
The present invention also provides an image-forming apparatus having the above process cartridge, and an intermediate transfer belt of the process cartridge.